> How do you address the argument, frequently made, that their terrorist designation is illegitimate
Then address that directly first. Ignoring the terrorist designation and going straight to not only voicing sympathy for them but outright supporting them isn’t something we want to encourage. (Note: I do not know if this activist supported Hamas.)
They usually do. They regularly begin with saying that they are advocating for peace with a foreign country that we have supported an illegitimate invasion into and that all claims of terrorism are just propaganda.
They usually don't dispute any of the atrocities there exists evidence for, they just insist that they are military acts of war by the armed forces of the Palestinian government and that terrorism is a category error, just like the Tet Offensive.
I fully support what you’re saying. It does not line up with my experience with pro-Palestinian protestors in New York City. (Or ACAB/Defund the Police before it. Same problem, in my opinion.)
Then address that directly first. Ignoring the terrorist designation and going straight to not only voicing sympathy for them but outright supporting them isn’t something we want to encourage. (Note: I do not know if this activist supported Hamas.)